Stainless Steel Alloy 864-SR (Stress relieved)
Heat-treated state
UNS S35135
Use when cold-formed bellows or springs need residual stress reduction and dimensional stability before hot service.
Values for the SR condition
Other Alloy 864 tempers and conditions
Alloy 864 is listed in 7 conditions; see the grade overview at Alloy 864.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Hot Rolled, Annealed and Pickled | Heavier sections for furnace fixtures, retorts and radiant tubes; slightly lower strength and coarser grain than cold-rolled annealed strip. | 270 | 600 | 45 | 165 HB | 1.7 % IACS |
AnnealedDefault Annealed (solution annealed, sheet/strip/tube) | Standard stocked condition: maximum ductility for bellows/flex-tube forming and best corrosion/oxidation performance. | 290 | 620 | 45 | 170 HB | — |
Cold drawn | Choose for close-tolerance bar and tube where higher yield strength and better surface finish are needed than annealed. | 520 | 760 | 25 | 20 HRC | 1.7 % IACS |
SRThis page Stress relieved | Use when cold-formed bellows or springs need residual stress reduction and dimensional stability before hot service. | 600 | 830 | 20 | 23 HRC | 1.7 % IACS |
Cold Worked, 1/4 Hard | Light temper for spring-back-controlled clamps, gaskets and formed parts needing extra stiffness. | 620 | 830 | 18 | 25 HRC | 1.7 % IACS |
Cold Worked, 1/2 Hard | Higher-strength strip/wire for clamps, mesh and springs used below the recrystallization range. | 760 | 965 | 10 | 31 HRC | 1.7 % IACS |
Cold Worked, Full Hard / Spring temper | Maximum strength condition for wire, springs and braid used in exhaust flex couplings; very limited ductility. | 965 | 1,150 | 5 | 36 HRC | 1.7 % IACS |
What is Alloy 864-SR?
Alloy 864-SR is Alloy 864 heat treated to SR — use when cold-formed bellows or springs need residual stress reduction and dimensional stability before hot service. Alloy 864-SR has a yield strength of 600 MPa (87 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 86% of stainless steel grades. Elongation at break is 20% and the elastic modulus is 197 GPa (28.6 Msi). Alloy 864-SR has a density of 7.94 g/cm³ (0.287 lb/in³), heavier than 78% of stainless steel grades. It melts at 1,355°C (2,471 °F). Annealed is the default condition FabDigit quotes; SR is available on request or by drawing note.
Advantages
- High strength — 600 MPa (87 ksi), better than 86% of stainless steel grades
Limitations
- Low electrical conductivity — 1.7 % IACS, worse than 98% of stainless steel grades
- Poor heat conductor — 11.5 W/m·K (6.64 BTU/hr·ft·°F), worse than 97% of stainless steel grades
- High embodied carbon — 7 kg CO₂/kg, worse than 96% of stainless steel grades
- Limited ductility — 20%, worse than 79% of stainless steel grades
Alloy 864-SR properties
Typical room-temperature values for Alloy 864-SR; 23 are specific to this condition. Other listed values are Alloy 864 reference data and may not represent this condition. Bars are the position among stainless steel grades.
Physical3
Alloy 864-SR has a density of 7.94 g/cm³ (0.287 lb/in³), heavier than 78% of stainless steel grades. It melts at 1,355°C (2,471 °F).
Mechanical14
Alloy 864-SR has a yield strength of 600 MPa (87 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 86% of stainless steel grades. Elongation at break is 20% and the elastic modulus is 197 GPa (28.6 Msi).
Thermal5
Alloy 864-SR is rated for continuous service to 600°C (1,112 °F). It conducts heat at 11.5 W/m·K (6.64 BTU/hr·ft·°F), worse than 97% of stainless steel grades. Thermal expansion is 14.4 µm/m·K (8 µin/in·°F).
Electrical3
Alloy 864-SR conducts electricity at 1.7 % IACS, worse than 98% of stainless steel grades.
Chemical & Environmental3
Corrosion resistance is good (57/100), worse than 66% of stainless steel grades.
Sustainability4
Producing a kilogram of Alloy 864-SR takes about 95 MJ of energy and emits 7 kg of CO₂ — more than 96% of stainless steel grades. Typical recycled content is 35%.
Manufacturability6
Alloy 864-SR's machinability is poor (29/100, worse than 76% of stainless steel grades); weldability good (68/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Alloy 864-SR
Is Alloy 864 easy to machine?
Machine like a Ni-Fe-Cr heat-resisting alloy: rigid setup, sharp positive-rake carbide, low speed / heavy positive feed to cut under the work-hardened layer, flood coolant, avoid dwelling.
Can Alloy 864 be welded?
Readily joined by GTAW/GMAW/PAW with matching or Ni-base filler (e.g. ERNiCrMo-3 / 82-type); keep interpass temperature low, no preheat required, no post-weld heat treatment normally needed.
Can Alloy 864 be formed, bent or molded?
Excellent cold formability for bellows, convolutions and deep-drawn parts; work-hardening rate is high, so plan intermediate solution anneals (~1065–1120 °C, rapid cool) for severe forming.
What surface finishes work on Alloy 864?
Pickle/passivate after hot work to restore the chromia film; takes a good mechanical and electropolished finish; no anodizing — plating or paint is rarely needed for exhaust/furnace service.
Alloy 864 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Niprimary austenite stabilizer, gives chloride-SCC and carburization resistance | 33 – 35 | 34 |
| Croxidation/scale resistance | 20 – 22 | 21 |
| Mopitting resistance and high-temperature strength | 3.5 – 4.5 | 4.2 |
| Ticarbide stabilization | 0.15 – 0.6 | 0.4 |
| Si | ≤ 1 | 0.5 |
| Mn | ≤ 1 | 0.5 |
| C | ≤ 0.05 | 0.03 |
| S | ≤ 0.02 | — |
| P | ≤ 0.03 | — |
| Febalance, approx. 37–40 % | balance | — |
Alloy 864-SR — frequently asked
What is Alloy 864-SR used for?
Alloy 864-SR is typically used for pyrolysis furnace tubing, high-temperature fixtures, radiant coils and carburizing furnace hardware. In short: best-forming heat-resistant superaustenitic; carburization-resistant furnace alloy; upgrade over 321/347.
What is the yield strength of Alloy 864-SR?
Alloy 864-SR has a typical yield strength of 600 MPa (87 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 86% of stainless steel grades. Strength varies by condition: see the 7 listed tempers.
Is Alloy 864-SR easy to machine?
Not especially — machinability is rated poor (29/100, worse than 76% of stainless steel grades). Machine like a Ni-Fe-Cr heat-resisting alloy: rigid setup, sharp positive-rake carbide, low speed / heavy positive feed to cut under the work-hardened layer, flood coolant, avoid dwelling.
Can Alloy 864-SR be welded?
Yes — weldability is rated good (68/100). Readily joined by GTAW/GMAW/PAW with matching or Ni-base filler (e.g. ERNiCrMo-3 / 82-type); keep interpass temperature low, no preheat required, no post-weld heat treatment normally needed.
What surface finishes work on Alloy 864-SR?
Pickle/passivate after hot work to restore the chromia film; takes a good mechanical and electropolished finish; no anodizing — plating or paint is rarely needed for exhaust/furnace service.
Can Alloy 864-SR be formed, bent or molded?
Excellent cold formability for bellows, convolutions and deep-drawn parts; work-hardening rate is high, so plan intermediate solution anneals (~1065–1120 °C, rapid cool) for severe forming.
What is the maximum service temperature of Alloy 864-SR?
Alloy 864-SR is rated for continuous use to about 600°C (1,112 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Alloy 864 Annealed and Alloy 864 CW-FH?
Annealed is the default condition — standard stocked condition: maximum ductility for bellows/flex-tube forming and best corrosion/oxidation performance. CW-FH: maximum strength condition for wire, springs and braid used in exhaust flex couplings; very limited ductility. Yield strength is 290 MPa in Annealed versus 965 MPa in CW-FH.
Sources
- INCOLOY alloy 864 (UNS S35135) technical bulletin — Special Metals Corporation (2004)
- ASTM B815 / ASTM A1058-family test practice and UNS S35135 registration — ASTM International / SAE-ASTM UNS (2020)
- ASM Handbook Vol. 1: Properties and Selection — Heat-Resistant Fe-Ni-Cr Alloys — ASM International (1990)
- ASM Specialty Handbook: Heat-Resistant Materials — ASM International (1997)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.